Liquid fuel pumping apparatus

ABSTRACT

A liquid fuel injection pumping apparatus including an injection pump which can supply fuel in turn to a plurality of outlet ports, each outlet port being connected by a pipeline to an injection nozzle, there being disposed in each outlet port a valve element which is spring loaded in one direction and which is moved by the action of fuel leaving the outlet port, to allow fuel to flow to the pipeline and the remote side of the valve element being subjected to a substantially constant pressure the arrangement being that the valve element will remain in the open position until the pressure in the outlet port has fallen to a predetermined value whereafter the element cuts off the communication between the pipe line and the port and the element acts to pressurize fuel contained in the port and the injection pump until the communication between the injection pump and the port is closed.

United States Patent [72] Inventor l l l l l l l Filed Patented Assignee Priority Appl. No.

Ivor Fence Greenford. England 833,606

June [6, I969 July l3, I971 C. A. V. Llmited bondon, England July 1, 1968 Great Britain 31261168 LIQUID FUEL PUMPING APPARATUS Primary Examinerl.aurence M. Goodridge AttorneyHolman & Stern ABSTRACT: A liquid fuel injection pumping apparatus ineluding an injection pump which can supply fuel in turn to a plurality of outlet ports, each outlet port being connected by a pipeline to an injection noule, there being disposed in each outlet port a valve element which is spring loaded in one direction and which is moved by the action of fuel leaving the outlet port, to allow fuel to flow to the pipeline and the remote side of the valve element being subjected to a substantially constant pressure the arrangement being that the valve element will remain in the open position until the pressure in the outlet port has fallen to a predetermined value whereafter the element cuts off the communication between the pipe line and the port and the element acts to pressurize fuel contained in the port and the injection pump until the communication between the injection pump and the port is closed PATENTED JUL! 3197: 3592.176

INVENTOE' rm ffiw ATTdENEYS LIQUID FUEL PUMPING APPARATUS This invention relates to liquid fuel injection pumping apparatus for supplying fuel under pressure to a multicylinder internal combustion engine and of the kind comprising an injection pump and a distributor which distributes fuel delivered under pressure from the injection pump during successive injection strokes thereof, to a plurality of outlet ports in turn, the outlet ports in use, being connected by pipe lines rcspectively to the injection nozzles of the engine.

Such pumps are provided with a form of control whereby the quantity of fuel which flows into the injection pump during successive filling strokes is substantially constant for a given setting of the control. The quantity of fuel delivered by the injection pump during each injection stroke should therefore be constant. In practice however differences in the quantity of fuel delivered are observed and these differences are thought to be due to the formation of cavities in the column of fuel between the injection pump and an outlet or due to over pressurization of the column of fuel. The cavities of over pressurization of the fuel occur due to pressure waves in the aforesaid pipelines.

The object of the invention is to provide such an apparatus in which the formation of cavities or the over pressurization of fuel is minimized.

According to the invention in an apparatus of the kind specified each outlet is provided with a control valve which comprises a valve element slidable axially within a cylinder, resilient means acting to urge the element towards one end of the cylinder, a port formed in the wall of said cylinder and which is uncovered to said one end of the cylinder during movement of the element against the action of the resilient loading, and passage means whereby the other end of the cylinder is connected to a substantially constant pressure which is lower than the pressure generated by the injection pump, the arrangement being such that at the start of injection of fuel the element is moved against the action of its resilient loading by the pressure of fuel generated by the injection pump to uncover the port and to permit fuel to flow to the en gine and at the end of injection of fuel the element remains in this position until the pressure of fuel has dropped to a predetermined value, the element then returning towards said one end of the cylinder thereby closing said port to maintain said predetermined pressure in the pipeline and also serving during its return motion to maintain the fuel remaining in the distributor and injection pump at the pressure until the outlet is closed.

In one example of an apparatus in accordance with the invention and as shown in diagrammatic form in the accompanying drawing, there is provided a body part in which is mounted a rotary cylindrical distributor member 11 which at one end is coupled to an injection pump 12. This is provided with a transversely extending bore and mounted within this bore is a pair of reciprocable pumping plungers which are arranged to be moved inwardly as the distributor member rotates, by the action of cam lobes formed in the internal periphery of an annular cam ring which surrounds the dis tributor member at this point.

The transversely extending bore is in communication with a longitudinal passage 13 extending within the distributor member and at one point this passage is in communication with a radially disposed delivery passage 14 which is arranged to register in turn and as the distributor member rotates, with a plurality of outlet ports 15 formed in the body part. The communication of the delivery passage 14 and one of the out let ports 15 occurs during an injection stroke of the injection pump and whilst the pumping plungers are being moved inwardly. Fuel is supplied to the injection pump 12 from a feed pump 16 having an inlet 17 and an outlet l8 formed in the body part and having its rotary part mounted on the distribu tor member. The outlet 18 of the feed pump is connected to an inlet port 19 formed in the body part 10 and which is positioned to register in turn with a plurality of inlet passages 20 formed in the distributor member and communicating at their inner ends with the longitudinal passage 13. The registration of an inlet passage with the inlet port occurs during a filling stroke of the injection pump and when the pumping plungers are allowed to move outwardly and the extent of outward movement is determined by a fuel control means 21 disposed intermediate the outlet of the feed pump and the aforesaid inlet port.

ln use, the distributor member is driven in timed relationship with the cnginc with which the apparatus is associated and the outlet ports are connected by pipelines 22 respectively to the injection nozzles 23 of the engine to which fuel is being supplied by the apparatus. Each nozzle incorporates a spring loaded valve to control the flow of fuel through the orifice of the nozzle and the arrangement is such that during inward movement of the plungers fuel under pressure will be supplied to one of the nozzles thereby opening the valve therein and allowing fuel to flow to the associated combustion space. At the end of the injection stroke the delivery passage 14 moves out of register with the outlet port 15 and an inlet passage 20 is moved into registry with the inlet port l9. Fuel then flows into the injection pump, the quantity of fuel being determined by the setting of the control means. Thereafter the cycle is re peated and fuel is supplied to the outlet ports in turn.

With such apparatus there is a risk of over pressurization of the fuel remaining in the passages of the distributor member and the injection pump before the delivery passage 14 moves out of register with an outlet port 15. In some cases however, instead of over pressurization, cavities are formed in the column of fuel between the outlet port and the injection pump. Both these effects have the overall effect that the quan tity of fuel delivered by the apparatus at each injection stroke varies in an undesirable manner even though the setting of the control means 21 remains constant. The cavities and over pressurization of fuel are thought to be created by pressure waves occuring in the aforesaid pipelines due to the closing of the spring loaded valve members of the nozzles.

in order to minimize the risk of cavities forming or over pressurization of fuel there is provided in each outlet, a control valve 24 the effect of which is to maintain the fuel con tained within the longitudinal passage and the delivery passage under pressure until the delivery passage has moved out of registration with the outlet. Furthermore, the control valve acts to maintain a predetermined residual pressure in the associated pipeline, The control valve comprises a cylinder 25 which is formed in the body part and in which is mounted a cylindrical valve element 26. One end of the cylinder is in communication with the outlet port 15 and formed in the wall of the cylinder is a circumferential groove 27 which constitutes a further port, and which communicates with the pipeline 22 and through which fuel flows to the injection nozzle. The valve element 26 is spring loaded towards said one end of the cylinder and the other end ofthe cylinder is in communication with a source of fuel at a substantially constant pressure which is lower than the pressure generated by the injection pump. Conveniently this source of pressure is the outlet 18 of the feed pump. In use, after the delivery passage has registered with an outlet 15, fuel under pressure from the injection pump acts on the end of the valve element 26 remote from the spring and moves it against the action of the spring. During this movement the groove 27 is uncovered and the element is halted by a stop peg 28. Once the groove is uncovered injection of fuel to the engine takes place as described above. At the end of the injection period the pumping plungers are allowed to move outwardly by suitable shaping of the cam lobes but during this movement the delivery passage remains open to the outlet port. Fuel therefore flows from the pipeline 22 through the cylinder and into the passages of the rotor. When the pressure of fuel falls to a predetermined value the element moves towards said one end of the cylinder and the groove is covered thereby preventing further flow of fuel from the pipeline. However, continued movement of the valve element occurs and during this movement fuel flows from said one end of the cylinder towards the transversely extending bore of the injection pump During this movement, however, the pressure of the column of fuel is maintained by the action of the valve element thereby minimizing the risk of the formation of cavities. The movement of the valve element under the influence of its spring loading is completed before the delivery passage moves out of register with the outlet port.

By this arrangement any fluctuations in pressure due to pressure waves oecuring in the pipeline are stabilized before the delivery passage is moved out of register with an outlet port so that variations in the quantity of fuel delivered by the apparatus to the engine during successive injection strokes are minimized.

lclaim:

l. A liquid fuel pumping apparatus for supplying fuel under pressure to a multicylinder internal combustion engine and of the kind comprising a body part, an injection pump in the body part, a plurality of outlet ports, formed in the body part and which in use, are connected by pipelines to the injection nozzles of the associated engine, a distributor in the body part and which distributes fuel delivered by the injection pump during successive injection strokes to the outlet parts in turn, a plurality of control valves for controlling the flow of fuel through the outlet ports respectively each control valve comprising a valve element slidable axially within a cylinder defined in the body part, resilient means acting to urge the element towards one end ofthe cylinder, passage means through which said one end of the cylinder is in communication with the associated outlet port. an escape port formed in the wall of said cylinder and which is uncovered to said one end of the cylinder during movement of the element against the action of the resilient loading by fuel under pressure flowing through the associated outlet port, or feed pump having an outlet from which fuel can flow to the injection pump, further passage means through which the other end of the cylinder is connected to the outlet of the feed pump, the arrangement being such that at the start of injection of fuel the element is moved against the action of its resilient loading by the pressure of fuel generated by the injection pump to uncover the escape port and to permit fuel to flow to the engine and at the end of the injection of fuel the element remains in this position until the pressure of fuel has dropped to a predetermined value. the ele ment then returning towards said one end of the cylinder thereby closing said escape port to maintain said predetermined pressure in the pipeline connected to the escape port and also serving during its return motion to maintain the fuel remaining in the distributor and the injection pump under pressure until the outlet is closed 2. An apparatus as claimed in claim l including stop means to limit the extent of movement of the element against the action of the resilient loadings 

1. A liquid fuel pumping apparatus for supplying fuel under pressure to a multicylinder internal combustion engine and of the kind comprising a body part, an injection pump in the body part, a plurality of outlet ports, formed in the body part and which in use, are connected by pipelines to the injection nozzles of the associated engine, a distributor in the body part and which distributes fuel delivered by the injection pump during successive injection strokes to the outlet parts in turn, a plurality of control valves for controlling the flow of fuel through the outlet ports respectively, each control valve comprising a valve element slidable axially within a cylinder defined in the body part, resilient means acting to urge the element towards one end of the cylinder, passage means through which said one end of the cylinder is in communication with the associated outlet port, an escape port formed in the wall of said cylinder and which is uncovered to said one end of the cylinder during movement of the element against the action of the resilient loading by fuel under pressure flowing through the associated outlet port, or feed pump having an outlet from which fuel can flow to the injection pump, further passage means through which the other end of the cylinder is connected to the outlet of the feed pump, the arrangement beIng such that at the start of injection of fuel the element is moved against the action of its resilient loading by the pressure of fuel generated by the injection pump to uncover the escape port and to permit fuel to flow to the engine and at the end of the injection of fuel the element remains in this position until the pressure of fuel has dropped to a predetermined value, the element then returning towards said one end of the cylinder thereby closing said escape port to maintain said predetermined pressure in the pipeline connected to the escape port and also serving during its return motion to maintain the fuel remaining in the distributor and the injection pump under pressure until the outlet is closed.
 2. An apparatus as claimed in claim 1 including stop means to limit the extent of movement of the element against the action of the resilient loading. 